Resection of mediastinal granulocytic sarcoma triggered the rapid progression of acute myeloid leukemia

Mediastinal granulocytic sarcoma (GS) is a relatively rare disease. We experienced a case of acute myeloid leukemia (AML) that took a rapid turn for the worse after the resection of a mediastinal GS. A healthy 60-year-old man had been in good general health all his life, but was diagnosed with a mediastinal tumor by his family physician and was referred to our department. The patient underwent resection of the mediastinal tumor because thymoma was highly suspected. On postoperative day (POD) 3, the patient suffered a fever as well as an elevated white blood cell (WBC) count and a high C-reactive protein level. His WBC count was 77,240 at its peak on POD 9, at which point the patient was diagnosed with AML by bone marrow aspiration. The immunohistological findings showed the features of leukemia, and GS was diagnosed. Despite chemotherapy, the patient died on POD 28 as a result of rapid disease progression.